Automatic telephone system



g- 1940- E. w. HULLEGARD 2,212,177

AUTOMATIC TELEPHONE SYSTEM Fil ed Nov. 9. 1937 h/ Wad e a llvv'em a y I The present invention telephone systems and has Patented Aug. 20, 1940 Erik Waldemar 'Hullegard, Stockholm, Sweden, assignor to Telefonaktiebolaget L. M. Ericsson,

Stockholm, Sweden.

a company of Sweden Application November 9, 1937, Serial No. 173,697

r I v In Sweden November 14, 1936 3 Claims.

relates to automatic for. its object to provide an arrangementin such systems rendering possible the connections automatic setting up of telephone between different lines over electronic or discharge paths, for example connections from. subscribers lines to link lines within a telephone exchange or vice versa. According to the invention said object is attained substantially by connecting each wire of a calling line over a resistance to a source of current having a voltage which differs from the voltage of the corresponding wire in the called lines.-

The invention is described more in detail having reference to the drawing attached to this specification and forming part thereof, which drawing shows as an example an application of the invention in an automatic telephone exchange.

A subscriber AI is connected to the exchange over a two-wire line ALI and AL2. In the exchange each wire of the line is connected in multiple to electrodes I of paths or tubes UI a number of discharge and U2, the other electrodes 2 of which are connected to a two-wire link line FLI and FLZ within the exchange.

According to the invention each one of the two branches of the subscribers line is also connected at a point 5 or 6 respectively over a resistance rI or T2 respectively to the plus-pole or minus-pole respectively of a battery El.

In each branch a resistance T3 or 14, which is connected in parallel with a condenser CI or C2, is included between the electrode I and the 6 for the battery. The

connecting point 5 and two branches of the link line are connected over resistances r5 and T6 to the plus-pole and second battery E2.

minus-pole respectively of a The voltage of the battery E2 differs from the voltage of the battery El.

The voltage difference of determined that it does not paths. Between in each discharge path a discharge and 2 there is provided grid 3 which is connected to a the two batteries is so cause ignition of the the two electrodes I marking line ML.

The switching operations taking place upon a call from the subscribers set AI scribed. When the subscriber AI micro-telephone, a circuit is closed scribers set, the subscribers line ALI, ALZ,

will first be delifts off his over the suband connecting points 5 and 6. The current passing through the resistance TI causes a drop of voltage resulting in a reduction in potential at the point 5 where the battery El is connected to the subscribers line ALI. The resistance TI is so dimensioned that said reduction of voltage will be sufficient to increase the voltage difference between the subscribers line ALI and the link line FLI to the ignition voltage for a discharge path UI. Since the two branches of the subscribers line are connected in multiple with a plurality of pairs of discharge paths special provisions must be made to insure connection between the other branch ALZ of the subscribers line and the branch FL2 of the same link line. For this purpose, discharge paths having different ignition voltages can be provided, for example, in the same sequence for both branches of the diiferent subscribers lines. Alternately, the ignition of one discharge path UI can be made to cause ignition of the corresponding discharge path U2, in that for example provisions can be made to ensure that the voltage E2 is applied on the corresponding link line branch only after the path UI has been ignited and the line FLI energized. Ignition of both paths UI and U2 completes the connection between the subscribers line and a link line in the exchange. The current now set up changes the potential of the wire so that no other subscribers line can be connected to the same link line, the current through the resistance r2 raising the voltage of the electrode l and of the electrodes connected in multiple therewith to such a degree that none of the discharge paths to which said latter electrodes appertain can be ignited. The same current causes also in the resistance r5 a voltage drop which lowers the voltage of the electrode 2 and of the electrodes connected in multiple therewith to such a value that no other discharge path appertaining to the link line FLI can be ignited. Busy marking is thus effected immediately.

The switching operations taking place upon a call intended for a subscriber AI are the following. A register or other switching device actuated upon a call from a subscriber by the numerical impulses marks in ordinary manner over lines ML the pair of discharge paths UI and U2 which connect the calling link line with the desired subscribers line. Over the marking lines ML the potential on the grids 3 of the discharge paths is changed so that said paths are ignited. Said marking occurs only during a brief moment. A ringing signal can be transmitted to the subscriber AI by generating oscillations in the tubes UI and U2, for example in cooperation with 'condensers and resistances, or by connecting a suitable ringing current source to the link line. A connection can also be set up from a link line to a subscribers line by changing the potential on the branches of the link line and by simultaneously changing the grid potentialin the corresponding discharge paths. The ignition of the discharge paths is then brought about through co-operation between said two changes of potential.

I claim:

1. A telephone exchange comprising, link lines at said exchange and subscriber lines connected to said exchange, discharge paths arranged between the corresponding speaking wires of said link lines and subscriber lines, a current source of certain voltage connected to each speaking Wire of a subscriber line over resistances, a second current source of another voltage connected to each wire of the link lines, the voltage difference between said current sources, being so determined that an increase of said voltage difference will cause ignition of the discharge paths to provide a direct connection between a link line and a subscriber line over said discharge paths, a resistance and a condenser arranged in parallel in each branch of a subscriber line between electrodes of the discharge paths and the points on the line in which the current source is connected.

2. A telephone exchange comprising, link lines at said exchange and subscriber lines connected to said exchange, discharge paths arranged between the corresponding speaking wires of said link lines and subscriber lines, a current source of certain voltage connected to each speaking wire of a subscriber line over resistances, a second current source of another voltage connected to each wire of the link lines, the voltage difference between said current sources being so determined that an increase of said voltage difierence Will cause ignition of the discharge paths to provide a direct connection between a link line and a subscriber line over said discharge paths, a grid in each discharge path, means for simultaneously changing the potential on the branches of the link line and the potential of the grids belonging to the discharge paths between said linkline and a subscribers line whereby the discharge paths are ignited upon a call from said link line to said subscriber line.

3. A telephone exchange com-prising, link lines at said exchange and subscriber lines connected to said exchange, discharge paths arrange-d between the corresponding speaking Wires of said link lines and subscriber lines, a current source of certain voltage connected to each speaking wire of a subscriber line over resistances, a second current source of another voltage connected to each wire of the link lines, and the voltage difference between said current sources being so determined that an increase of said. voltage difference will cause ignition of the discharge paths to provide a direct connection between a link line and a subscriber line over said discharge paths.

ERIK WALDEMAR HULLEGZKRD. 

